1. Field of the Invention
The invention relates to glass fiber reinforced polycarbonate compositions and molding compositions, which are distinguished by high rigidity, high flowability, high processing stability, good chemical resistance and good aging resistance vis-a.-vis the effects of light and heat compared with the prior art.
2. Description of Related Art
Compositions containing polycarbonate and rubber-modified styrene polymers, such as e.g. ABS (acrylonitrile-butadiene-styrene polymers), are known for their balance of excellent mechanical properties and good melt flowability. They are used in many different areas of application, for example, in car construction, in the building sector and in housings for office equipment and domestic appliances.
A low coefficient of thermal expansion and good dimensional stability, as well as shape stability and high rigidity, are generally needed to produce moulded parts with a large surface area. These properties can be achieved by the addition of fillers or reinforcing materials. High moduli of elasticity can be obtained particularly by adding fibrous reinforcing materials. However, the addition of the fillers or reinforcing materials generally has a disadvantageous effect on the toughness and particularly on the flow properties of the polymer melts, i.e. the processing characteristics. As a result, increased processing temperatures are usually required, which entails a further reduction in material toughness. The practicable degrees of filling with reinforcing material, and thus the material rigidities that can be achieved are, in effect, limited by these parameters, and moulded parts with large surface areas and very thin walls are often impossible to produce with those polycarbonate compositions that correspond to the prior art described below. For these areas of application there is a demand for such polycarbonate compositions to be produced with improved flowability and a higher modulus of elasticity, and with a toughness which is good over a broad processing window and stable vis-à-vis heat aging. Since moulded parts produced from compositions of this type are often painted and, in the context of the post-treatment needed in connection with this, generally come into contract with chemicals, such as e.g., paint solvents, there is a further demand for adequate chemical resistance. For this reason, the use of low molecular weight polycarbonates to improve the polymer melt flowability is out of the question, since these usually lead to a negative effect on stress cracking resistance.
Rubber-modified vinyl copolymers containing glass fiber reinforced polycarbonate compositions are known from the prior art.
WO-A 00/39210 discloses polycarbonate compositions containing polycarbonate, styrene resin, phosphoric ester and reinforcing agents (e.g. glass fibers), as well as optionally a graft polymer based on a silicone-acrylate composite rubber with a vinyl monomer-based graft shell, which are distinguished by improved hydrolysis resistance, good flame resistance and by improved mechanical properties. The styrene resins employed contain a rubber-based graft polymer. No glass fiber sizes are disclosed.
EP-A 1 240 250 discloses polycarbonate compositions containing 10-93 wt. % polycarbonate, 3-50 wt. % rubber elastic-based graft polymer, 3-50 wt. % thermoplastic copolymer and 1-20 wt. % of a mixture of particulate mineral and fibrous fillers, which are distinguished by reduced thermal expansion, good toughness, good dimensional stability and high flowability together with improved surface quality in the region of the gate.
EP-A 0 624 621 discloses polycarbonate compositions containing 10-80 wt. % polycarbonate, 10-80 wt. % rubber-modified graft polymer and 5-50 wt. % glass fibers with a coating containing polyolefin wax, which are distinguished by improved toughness and ductility.
EP-A 0 345 652 discloses polycarbonate compositions containing 10-75 wt. % polycarbonate, 10-50 wt. % rubber-based graft copolymer, up to 50 wt. % styrene copolymer, 0.5-50 wt. % terpolymer containing tert-butyl (meth)acrylate and 5 to 50 wt. % reinforcing agents (e.g. glass fibers), which are distinguished by high distinguished by high strength, good toughness and by low yellowing. The glass fibers used in this cited application are generally provided with a size and an adhesion promoter, but the composition of the size is not disclosed here.
The prior art documents cited above do not, however, disclose any compositions that contain polycarbonate, rubber-tree vinyl copolymers (e.g. styrene-acrylonitrile copolymers) and no rubber-containing graft polymer or only very small quantities thereof (i.e. up to 2 wt. %).
Disadvantages of the compositions described in the prior art, which contain rubber-modified graft polymers in quantities of more than 2 wt. %, are too low a melt flowability and inadequate aging resistance.
Compositions containing polycarbonate, glass fibers and rubber-free vinyl copolymer, which contain no rubber-modified vinyl copolymers or only very small quantities thereof, are also known from the prior art.
WO-A 84/04317 discloses polycarbonate compositions containing polycarbonate, styrene resin, unsized glass fibers and a hydrogen polysiloxane, which are distinguished by high impact resistance and a high modulus.
EP-A 0 647 679 discloses polycarbonate compositions containing special copolycarbonates with bisphenol and resorcinol monomer units, rubber-containing copolymer and/or copolymer of vinyl aromatic and cyanated vinyl monomer components as well as inorganic filler (e.g. glass fibers), which are distinguished by good flowability, high impact resistance and good surface quality. No glass fiber sizes are disclosed.
EP-A 1 038 920 discloses polycarbonate compositions substantially consisting of a special aromatic polycarbonate produced by melt polymerization, a styrene-based resin (e.g. a styrene-acrylonitrile copolymer with a styrene content of at least 20%, preferably at least 30%), a reinforcing fibrous filler and optionally an elastomeric polymer, which are distinguished by improved moist beat resistance and improved toughness. It is disclosed that the glass fibers used may be coated with a size made of polymers (such as e.g. epoxy resin, urethane resin, acrylic resin, nylon resin etc). In the examples, only compositions containing polyurethane-sized glass fibers are disclosed.
WO-A 2006/040087 discloses polycarbonate compositions containing polycarbonate, a terpolymer of styrene, acrylonitrile and maleic anhydride, and long glass fibers, which are distinguished by a combination of improved tensile strength, modulus of elasticity and impact resistance. In addition, these compositions preferably contain at least one polymer selected from the group of the rubber-containing graft polymers and robber-free copolymers. It is disclosed that the long glass fibers may be surface-modified with a size, without any information on the chemistry of the size being disclosed.
Although the glass fiber reinforced polycarbonate composition based on rubber-free styrene resins disclosed in the prior art do generally exhibit good melt flowability and aging resistance, they are, however, distinguished by inadequate toughness for certain areas of application, particularly at higher processing temperatures, and by unsatisfactory chemical resistance and rigidity.